Full-duplex communication and half-duplex communication are available as communication methods used between a network apparatus (such as, e.g., a layer 2 switch or a router) connected to a network (such as, e.g., an Ethernet network) and a terminal apparatus (such as, e.g., a personal computer (PC) or a server). One of the full-duplex communication, the half-duplex communication, and an auto-negotiation is set on a port of each apparatus. Conventionally, if the auto-negotiation is set on a communication source apparatus and the full-duplex communication is set on a communication destination apparatus (also referred to as a link partner), the port set for auto-negotiation is set actually set for half-duplex. Accordingly, a communication method incompatibility takes place in the conventional scenario described above.